Objectionable current

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Pierre I've already corrected my own error. But what I'm saying now is that a circuit breaker on the supply side of a meter will be able to protect against any short circuit inside the meter enclosure. The new change in the 2008 NEC should cover this. Meter disconnects are now required to interrupt the circuit. I was under the impression that interrupt in this case means opening the circuit whenever a fault occurs. If the hot lead touches the meter enclosure the current will flow downstream first to the service disconnect and then back through the neutral to the utility transformer. The circuit breaker acting as meter disconnect will trip.
 
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Eric it is my understanding the meter disconnect switch must be capable of being manually opened under fault conditions. I may be mistaken about this. :smile:

In my experience the power company, not the installer decides where the metering equipment is located in relation to the service disconnecting means.

Sometimes they want 'hot sequence' metering, that means the meter is before the service disconnect and there is no easy way to kill the power to the meter without the power companies assistance.

Utility supply > meter > service disconnect > overcurrent protection > customer loads.

However more recently the power companies have been asking for 'cold sequence' metering requiring a disconnecting means ahead of the meter.

At first look we say great.

Utility supply > service disconnect > overcurrent protection > meter > customer loads.

But there is a problem, in that arraignment many power companies want to seal and lock the service disconnecting means enclosure to prevent tampering and theft. This can make the overcurrent protection inaccessible to the customer which is an NEC violation. The solution is the meter disconnect.

Utility supply > meter disconnect > meter > service disconnect > overcurrent protection > customer loads.

:smile:
 
If the meter disconnect is the property of the utility then they may have a right to do that. But not the service disconnect. You see in this configuration we have disconnects on both sides of the meter. Look at the definition for interrupting rating in Art.100. The device is intended to interrupt the circuit at that rating.
 
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erickench said:
If the meter disconnect is the property of the utility then they may have a right to do that. But not the service disconnect. You see in this configuration we have disconnects on both sides of the meter.
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In my area the equipment is owned and installed by the customer.

But the power company has the 'right' to do pretty much whatever they want under the terms of service that the areas utility commission has approved and the customer has agreed to.

In other words, the customer can refuse to allow the power company to lock the equipment but at that point the power company can refuse to supply that customer.
 
Well I don't know how it is in your area but here in New York City theft of electric service is fairly common. It seems that Con Edison is unable to turnoff the power from their own transformer unless they come on your property with a court order and take out the meter. I know the gas companies do that.
 
erickench said:
Well I don't know how it is in your area but here in New York City theft of electric service is fairly common.
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No doubt every area is different, I would never try to dispute that. :smile:

In my area we have many different utility companies, the main one is NStar but many towns have their own 'not for profit' municipal power providers. The rules and how each company enforces them are very different.

In one area the metering equipment may be wide open to anyone, a few miles away you may find hardened steel locks installed on all enclosures containing unmetered conductors. Some power companies do not even allow conduit bodies in the raceways containing unmetered conductors.

Here the customer must purchase the meter socket or CT cabinet but they must be from a list of approved equipment from the power company. All of these will have the neutral firmly connected to the enclosure.
 
iwire said:
Here the customer must purchase the meter socket or CT cabinet but they must be from a list of approved equipment from the power company. All of these will have the neutral firmly connected to the enclosure.
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Well if that's the case then you would have a parallel current path between the meter enclosure and service disconnect unless you remove the main bonding jumper from the service disconnect enclosure. This would violate the NEC of course.
 
erickench said:
Well if that's the case then you would have a parallel current path between the meter enclosure and service disconnect unless you remove the main bonding jumper from the service disconnect enclosure. This would violate the NEC of course.
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Parallel paths on the line side of the service disconnect are permitted by the NEC rules. The grounded conductor is used for all bonding and grounding purposes on the line side of the service disconnect.
 
erickench said:
If the meter disconnect is the property of the utility then they may have a right to do that. But not the service disconnect. You see in this configuration we have disconnects on both sides of the meter. Look at the definition for interrupting rating in Art.100. The device is intended to interrupt the circuit at that rating.
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Both switches and OCPDs have interrupting ratings. There is nothing in the definition of "interrupting rating" that would require the device to be an OCPD.
 
Well if that's the case then the equipment on the line side of the service disconnect will never be protected and bonding the neutral to the meter enclosure is not gonna accomplish anything. The fault must occur on the load side of the OCPD. If anything bonding the neutral to the meter enclosure will shunt out any fault current that may flow though a person's body.
 
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erickench said:
Well if that's the case then the equipment on the line side of the service disconnect will never be protected and bonding the neutral to the meter enclosure is not gonna accomplish anything. The fault must occur on the load side of the OCPD. If anything bonding the neutral to the meter enclosure will shunt out any fault current that may flow though a person's body.
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That is exactly one of the reasons, the other is to cause the SEC's to burn free, I know this sounds crazy but it has been this way for a long long time.
 
erickench said:
Well if that's the case then the equipment on the line side of the service disconnect will never be protected and bonding the neutral to the meter enclosure is not gonna accomplish anything. The fault must occur on the load side of the OCPD.
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Exactly.

This is why the bonding jumpers are sized based on the service conductor sizes (250.66) and not the over-current device size (250.122).

The bonding jumpers have to handle large amounts of fault current.




If anything bonding the neutral to the meter enclosure will shunt out any fault current that may flow though a person's body.
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It will lessen the voltage potential between earth and the meter socket enclosure but I doubt it will reduce it to safe levels.

As Hurk mentioned the most likely thing to happen will be the utilities smaller NESC sized conductors to burn free from the customers larger NEC sized conductors.


Luckily that burning will be outside underground or outside overhead.

:smile:
 
Well if it melts the meter socket then maybe we should stop doing it. The connecting conduit from the meter to the service disconnect provides a fault current path through the main bonding jumper. If not then use a ground wire.
 
erickench said:
Well if it melts the meter socket then maybe we should stop doing it. The connecting conduit from the meter to the service disconnect provides a fault current path through the main bonding jumper. If not then use a ground wire.
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I really don't know what got you on this path, but you seem to have been all over the place. I haven't really determined if you have settled on an ultimate goal or not. Maybe you are just trying to learn about services through the discussion. Maybe there is a point you are trying to reach. Maybe you are just talking about this for general conversation. I'm not sure.

What does seem clear is that you have not had much exposure in this area or are at least unfamiliar with parts of it. But you have come to the right place as there are plenty of folks here that can help you learn. It is a great site for learning and keeping your knowledge fresh.
iwire said:
All of these will have the neutral firmly connected to the enclosure.
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That's the way they are here as well.
 
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